This research study involves participants who have acute lymphoblastic or acute myelogenous leukemia that has relapsed or has become resistant (or refractory) to standard therapies. This research study is evaluating a drug called KPT-330. Laboratory and other studies suggest that the study drug, KPT-330, may prevent leukemia cells from growing and may lead to the destruction of leukemia cells. It is thought that KPT-330 activates cellular processes that increase the death of leukemia cells. The main goal of this study is to evaluate the side effects of KPT-330 when it is administered to children and adolescents with relapsed or refractory leukemia.